Drilling bits for boring holes and wells

ABSTRACT

A novel drilling bit constituted by a cylindrical roller having a diameter which is smaller than the diameter and larger than the radius of the drilled hole. The roller is rotatably mounted on a tubular shaft which is parallel to but displaced eccentrically with respect to the axis of the drill stem and armed on the flat cutting face thereof with cutting elements and peripheral teeth, protection against radial wear being provided by anti-abrasive elements incorporated in the surface of the cylindrical zone which forms an extension of the teeth. A drill-sten connector which is coaxial with the hole balances the eccentric displacement of the roller by means of eccentric masses which are protected against wear and is provided with a duct for drilling fluid.

United States Patent Lazayres Jan. 21, 1975 ..175/333 Bennett............................... 175/343 XXX 669 779 333 555 777 111 2,877,988 3/1959 Cameron et al. 2,911,196 11/1959 Cameron et al. 3,174,563 3/1965 Edblom et al. 3,424,258 1/1969 Nakayama 3,429,390 2/1969 Primary Examiner-David H. Brown Activities Petrolieres (ELF), Paris, France Attorney, Agent, or Firm-Cameron, Kerkam, Sutton,

Stowell & Stowell 22 Filed: July 27,1973

21 Appl. No.: 383,316

[57] ABSTRACT A novel drilling bit constituted by a cylindrical roller having a diameter which is smaller than the diameter and larger than the radius of the drilled hole. The roller is rotatably mounted on a tubular shaft which is parallel to but displaced eccentrically with respect to the axis of the drill stem and armed on the flat cutting face thereof with cutting elements and peripheral teeth, protection against radial wear being provided by anti-abrasive elements incorporated in the surface of the cylindrical zone which forms an extension of the teeth. A drill-sten connector which is coaxial with the hole balances the eccentric displacement of the roller by means of eccentric masses which are protected 7 66 9 B @7339 3 3 9 /9 a 6 2 7 7 1 2 1 ,m3 m m E 3 a H 036N214 S D m as TN.- n 7 u a mm m mm B l m 1 3 T w H 7 n/ 8A r. n 4 "53 t P U 3 74 .lDi 13 CS n u 5 S 0 7 u a E e 7 .3 9 1 C 1 "3 C m m m h :0 H W m mmfi H n m any E 9 W87 T .W "S1. .1. m L I... N 0 C m U F a. .M u 5 mm A U IF 1 1: 1 2 100 6 3 5 5 .1 1 [1. .1

1,334,632 3/1920 Pickin 1,906,056 2,511,831

against wear and is provided with a duct for drilling fluid.

4/1933 Golish....

2,619,325 Arutunoff...........,........... 175/330 X 17 Claims, 6 Drawing Figures 2,667,334 Ortloff...................

PATENTEU m2] ms SHEET 10F 2 FIG? FIG. 1

. l DRILLING BITS FOR BORING HOLES AND WELLS This invention generally relates to bits for boring or drilling wells in the earth.

One of the most difficult problems is the destruction of the central portion of the circular working face which is cut by a drilling bit since the cutting element such as teeth, studs or diamonds have impact or cutting velocities which are progressively lower in this zone until they become zero at the centre.

The resultant decrease in penetration capacity of the central portion can be compensated only by an increasing load per cutting element. In fact, it is precisely at the centre that it proves difficult to increase the number or to consolidate the cutting elements owing to the small space available and owing to the presence of irrigation ducts which usually open at the centre of massive drilling bits.

On the other hand, both'in the case of massive drilling bits and in the case of roller rock bits such as tricone rock bits, the mode of operation of the peripheral calibrating guard is also irrational since it is precisely those portions of the armour such as the external guards of diamond tools or the heels of rollers, the design function of which is to centre and guide the portion which directly cuts the working face of the drilled hole without resulting in wear, which are endowed with the maximum linear velocity with respect to the rock and are thus subject to the maximum risk of wear.

Another weak point of conventional drilling bits arises from the fact that each destruction element of the bit such as a tooth or diamond progresses along its own circular path.

Only one element need consequently lose its efficiency as a result of wear or failure for the entire feed tube affected as a result until the corresponding zone is overloaded and put out of action, this phenomenon being particularly marked in the case of diamond bits, a considerable proportion of which becomes unfit for use as a result of the so-called torage phenomenon.

Finally, the need to pass the cuttings beneath the peripheral cutting elements results in re-grinding which affects the useful life and power efficiency of the bit.

In order to overcome each of these disadvantages separately, many solutions have already been proposed.

Thus, in order to increase the armoured surface of the tool, the cutting elements have been distributed over cylindrical or conical rollers rotatably mounted on pins which are either parallel or inclined with respect to the drill stem which drives the tool.

In order to increase the cutting speed in the central zone, there have been constructed drilling bits comprising a single roller which is advantageously of approximately spherical shape and rotates about an axis which is inclined with respect to the axis of the drilled hole.

In the case of massive drilling bits and in particular diamond bits, it has been endeavoured to improve the destruction of the centre by providing the initial cutting zone with a cross-sectional area which is smaller than that of the drilled hole and centred on an axis which is parallel to the axis of the driving drill-stem, said stem being in turn centred within the drilled hole by means of centring devices or guides located above the drilling bit.

It has also been sought to replace the conventional formation-cutting at right angles to the working face by a more efficient lateral milling-cutting operation performed by rollers, said rollers being caused to rotate about axes which are displaced off-centre with respect to the axis of the hole and driven either directly or by reaction of the formation and in rotation about said axis. This is the case in particular of planetary drilling" by means of sets of at least two underground motors which are coupled in parallel.

One aim of the invention is to cumulate these different advantages in a novel combination which results in an improvement over each of the existing design solutions.

A further object is to combine the advantages provided by the teeth of the rotary rollers with those of the tools which are set with cutting or grinding elements such as diamonds or anti-abrasive inserts by making use of teeth in the zone of low cutting speeds, and by mak-- ing use of diamonds or the like in the zone of high linear cutting velocities.

The invention is directed to a drilling bit constituted by a cylindrical roller having a diameter d which is smaller than the diameter D of the drilled hole but larger than the radius of this latter, said roller being rotatably mounted by known means on a tubular shaft which is parallel to the axis of the drill stem,.the eccentric displacement e of said shaft being equal to the difference R r between the radius of the drilled hole and the radius of the roller, said roller being armed on the flat cutting face thereof with cutting or grinding elements after the fashion of conventional massive or diamond tools and with armed peripheral teeth which operate on the rolling principle in the same manner as the teeth of a tricone roller rock bit with the added advantage that a wear reserve can readily be formed by lengthening the peripheral teeth in a direction parallel to the axis by protecting these latter from radial wear by means of anti-abrasive elements which are incorporated in the surface of the cylindrical zone which forms an extension of said teeth.

Irrigation is advantageously carried out from a central opening of the roller and the jet which washes the working face can be preferentially oriented, for example in the direction of feed of the roller.

A further advantage over roller bits having inclined axes lies in the fact that the bearings and thrustbearings of the rolling or sliding type can readily be given all the axial space which is necessary to ensure optimum performance and in particular to extend their length of service by providing them with a leak-tight and efficient lubricating system.

By virtue of its definition and the planetary motion in the direction opposite to the rotary driving motion transmitted to the roller, the speeds of its cutting elements with respect to the formation are accordingly reduced in the peripheral zone and increased in the central zone in comparison with an identical tool which produces a drilling action by rotation about its axis.

The cutting velocity at any given point of the cutting face varies during one revolution between maximum and minimum values which can fall to 0 at the periphery. Only the centre of the roller describes a circle at constant velocity whilst the other points move in such a manner as to describe hypocycloids or shortened hypocycloids.

This particular feature makes it possible to cut the periphery by means of a rolling action and the face by means of an abrasive action even in the case of driving at the high'speeds of underground motors.

Good operation of an eccentric tool is clearly possible only if this latter is statically and dynamically balanced.

The tool in accordance with the invention therefore comprises as an integral portion a connector in which the weight distribution about the axis of the drilled hole balances the eccentric displacement of the roller in much the same manner as an engine crankshaft and provides at least two complementary peripheral bearing points which afford angularcompensation for the unilateral thrust to be applied by the roller on the wall of the hole during the drilling process, the assembly being carried out by known means which ensure angular positioning and axial continuity of the complete unit.

A better understanding of the invention will be gained from the following description of one embodiment, reference being made to the accompanying drawings which are given by way of example without any limitation being implied, and wherein:

FIG. 1 is a fragmentary vertical sectional view of a drilling-tool unit having a cylindrical roller in accordance with the invention and mounted on its balancing connector;

FIG. 2 is a bottom view of the same unit;

FIG. 3 is a transverse sectional view taken along line lll-lll of FIG. I;

FIG. 4 is a transverse sectional view taken along line lV-lV of FIG. 1;

HO. 5 is a diagram showing a relative position of th roller within the drilled hole as defined by the point A of contact of said roller with the wall;

H6. 6 is the corresponding diagram of the paths as described on the working face by successive and uniformly distributed points of the diameter of the roller which passes through the point A.

FIGS. 1 to 4 represent the case of a roller having a diameter d which is equal to thirty-one fortieths of the diameter D of the drilled hole, said roller being mounted on a connector provided with two guiding balance-weights which are each centred angularly at 120 on each side of the generating-line of contact of the roller with the wall of the drilled hole.

The corresponding eccentric displacement of the axis X of the roller with respect to the axis X of the connector and of the hole as shown in FIG. 1 will therefore be e D d/2 9/80 D. ln the example shown, the drilling tool proper is constituted by a crown l, the flat bottom face of which is treated in the same manner as a conventional massive tool provided with wings or segments 4 armed with cutting elements such as inset diamonds, a diamond concretion or anti-abrasive studs, inserts and the like which are irrigated by ducts as represented in the figure by a radiating fan system 5.

The crown is provided around its perimeter with teeth 3 which are similar to the teeth of tricone roller bits and armed in a comparable manner, said teeth being intended to destroy the periphery of the working face by rolling action. However,'the particular feature of this arrangement lies in the fact that theupward extension of said teeth constitutes a wear reserve as the bottom corner is worn away. In the line of extension of said teeth, the crown is armed with anti-abrasive inserts which will preferably be set with diamonds so as to ensure calibration of the hole and protection of the peripheral cutting elements.

The crown is mounted in a conventional manner as in the case of diamond tools on a skirt 2 which is in turn protected by anti-abrasive inserts, segments or built-up portions.

The unit described in the foregoing is provided in accordance with the example shown in the figure with a ball race 8 and with a protective skirt l8 and is mounted on a shaft 6 on which said unit rolls by means of rings of rollers such as those designated by the references l0 and ll, axial thrusts being carried by ball thrust bearings such as the bearings 7 and 9.

Axial locking of the roller 1 2 on the shaft 6 is effected in accordance with a known method by means of a ring of balls 12 which are introduced through a passageway, said passageway being closed after assembly by means of a plug 13 located at a point at which the balls are not under load as they pass.

In the case of the tool according to the invention, the plug aforesaid is clamped by the discharge nozzle 14 which is screwed into the axial passage of the shaft 6 by means of an internal octagonal nut 15. Said discharge nozzle is illustrated in the form of a cylindrical tube which conveys the irrigation fluid to the level of the irrigation ducts of the working face of the roller; at the outlet, the stream of fluid can be directed selectively along a given path, for example in the direction of angular displacement of the roller, this being achieved by modifying the discharge nozzle 14 which is reduced to a semicircle or to an elongated slot, for example.

Whether the bearings and thrust-bearings are of the roller and ball type as shown or of the sliding type, the bearings considered as a whole will advantageously be provided with a lubrication system which is in pressure equilibrium with the surrounding atmosphere, a plastic reservoir 16 being housed within the head of the member 6 so as to supply all the rotary bearings and being protected by means of seals such as the seal 17.

During the course of drilling operations, the reserve supply of lubricant can be completed by means of an injection valve 19 completed by a corresponding drainoff valve which is not shown in the figures.

The bearings and thrust-bearings which are shown in the drawings can be replaced without thereby departing from the invention by conical bearings or axial stacks as employed in turbodrills. Similarly, the seals can consist of rotary seals having flat faces.

After assembly, the units 1 2 6 is screwed and welded onto a connecting head 20 which is in turn connected in such a manner as to-ensure angular positioning with the centring body 26, said body being then connected to the drill pipe by means of a screw-thread 31.

As shown in axial cross-section in FIG. 1 and in transverse cross-section in FIG. 3, the connection of the head 20 to the body 26 is obtained by insertion of two eccentric cylindrical bearing elements 23 and 24, axial cohesion being ensured by means ofa single or multiple tensioning member such as the rod 33 which is screwed into the head 20 and tensioned by means of a nut 34 having multiple sides and resting on a seat 35 which is inserted in a bore 32 of the connector 26, the nut 34 being locked in position after tightening by means of a flanged washer 36.

Leak-tightness between the head and the body 26 is ensured by means of one or a number of O-ring seals such as the seal 25.

Circulation of drilling fluid is carried out through the bore 28 and a series of ducts 21 and 22 which are pierced in the connecting head 20 and open into a collecting chamber which is formed inside the head 20.

Guiding and centring of the connector 26 are carried out by means of shields such as those designated by the references 29 and 30, the shield 30 being not shown in cross-section l, or alternatively by means of sets of straight or helical blades which are commonly employed for this purpose. Said shields or blades are fitted with antiabrasive elements which serve at the same time as weights for balancing the unit consisting of drilling bit and connector.

This mode of assembly makes it possible to replace or to re-condition any elements of the drilling bit and connector unit between two periods of service; said unit can in turn be of single-unit construction or constituted by a plurality of elements connected together in axial relation. If necessary, the connector can advantageously be of the type comprising helically disposed segments as described in French Pat. No. 1,297,304 or alternatively of the roller type as described in French Pat. No. 1,280,063.

- During service, the connector which is centred in principle at the top by means of centring members disposed along weighting rods is maintained in the axis of the drilled hole by the succession of peripheral bearing points 30, 29 or equivalent means and the bearing generator-line of the roller.

' A particular feature which arises from the invention is the layout of the paths along which the various points of the cutting face of the drilling bit travel over the working face.

lt is known that, in the case ofa ratio: d D 2, each point of the perimeter of the roller describes a diagonal line of the circle D during rotational motion. lfd: D 2 3, the hypocycloid of each point of the perimeter has three cusps at l20; and if d D 3 :4, four cusps; and more generally when d D (x l) :x, there is thus a curve having x vertices which are located on the circle D.

In order to illustrate the shapes of the cutting element paths, a ratio ofd D 3 4 has been adopted in FIGS. 5 and 6; but for the actual construction of a tool, preference will be given to a ratio between two successive values of (x l) :x in order to prevent the cutting elements from falling back into the same paths if the roller were to roll over the external wall without sliding.

HO. 5 shows a starting position of the perimeter of a roller having a ratio d D 3 :4 starting from a point of contact A with the circle having a diameter D on which said roller travels.

In FIG. 6, there are shown on each side ofa diameter Y Y, respectively within the semi-circle l and in full lines the paths described by cutting elements such as diamonds which are placed at A B C D on the diameter A A of the roller between the contact point A and the centre M of said roller at distances r, 3r/4, r/2, r/4 and, within the semi-circle ll in dashed lines, the corre sponding paths of the points which are symmetrical Kinematic analysis shows that each of the points A B C D or E F G H moves along its path at a variable velocity v. Thus, the point A starts from v 0 at the cusps which are located on the perimeter of the surface being drilled and passes through a maximum velocity halfway between A and A; only the centre M of the roller describes a circle having a radius e at the uniform driving velocity.

While the roller travels along the segment A H A of the circle having a diameter D. the point A only describes the hypocycloid are A a A, namely less than one-third of the distance travelled by the roller.

FIG. 6 clearly brings out the density of sweeping of the central zone and shows that the mean linear velocity of the peripheral points is lower whilst that of the central points of the roller is higher than the linear velocites which the same points would have in a uniform circular motion.

It is also found that provision can be made within the roller for an axial duct having a radius which can range in value up to e D d without having any adverse effect on the sweeping of the axial zone of the workingface.

Modifications can be made in the embodiment hereinbefore described within the definition of equivalent technical means without thereby departing either from the scope or the spirit of the invention.

What we claim is:

l. A bit for drilling wells in the earth, of the type comprising a cylindrical roller having a diameter smaller than the diameter of the drilled hole and larger than the radius of said hole, a flat cutting face on said roller said roller perpendicular to the axis of said roller, irrigated destruction means on said face, armed teeth for said roller around its perimeter said roller being surmounted on the external cylindrical surface by segments which are protected against wear by antiabrasive elements, said roller being mounted to rotate freely on a tubular shaft having a geometrical axis which is parallel to that of the drilled hole and displaced off-centre with respect to said hole, a connector, a tensioning member maintaining said connector in said geometrical axis, said shaft being connected parallel to the axis of; and in angularly positioned relation with said connector, said connector having a geometrical axis which coincides with the axis of the drilled hole, a duct in said connector for the irrigation of the bit, means at the end of said connector remote from the tool for coupling with the drill stem, external eccentric masses on said connector protected against wear on the peripheral face thereof by anti-abrasive elements, said masses centering said connector within the drilled hole, compensating for the reversing couple exerted by the bit on said connector shaft during drilling and providing static and dynamic balancing of the tool-connector assembly during the drilling operation.

2. A drilling bit in accordance with claim I, wherein the cutting face of the roller is irrigated from an axial duct.

3. A drilling bit in accordance with claim 1, wherein the drilling face is armed with inset diamonds.

4. A drilling bit in accordance with claim 1, wherein the cutting face is armed with inserts of anti-abrasive material.

5. A drilling bit in accordance with claim 1, wherein the cutting face is armed with a diamond concretion.

6. A drilling bit in accordance with claim I, wherein the peripheral teeth are armed with anti-abrasive builtup portions.

7. A drilling bit in accordance with claim I, wherein the armour of the peripheral teeth comprises diamonds.

8. A drilling bit in accordance with claim 1, wherein the armour of the peripheral teeth comprises antiabrasive inserts.

9. A drilling bit in accordance with claim I, wherein the rotary roller is mounted on the shaft by means of thrust-bearings and ball-bearings.

10. A drilling bit in accordance with claim 1, wherein the ball-bearings and thrust-bearings work in a bath of lubricant in pressure equilibrium with the surrounding fluid from which said bearings are isolated by means of two rotary seals.

11. A drilling bit in accordance with claim 1, wherein the shaft of the tool is secured in the body of said connector by two superposed cylindrical bearing elements displaced in eccentric relation to each other.

, 12. A drilling bit in accordance with claim 1, wherein the tensioning member is put under tension by means of a locking nut which is accessible from that end of the connector which is remote from the roller.

13. A drilling bit in accordance with claim I. wherein said masses are two balancing weights protected against abrasion and located at angles of and 240 from the generating-line of contact of the roller with the wall of the drilled hole.

14. A drilling bit in accordance with claim 13. wherein said weights are distributed to provide static and dynamic balancing of the roller and the connector assembly.

15. A drilling bit in accordance with claim I, wherein the roller is keyed on its shaft by means ofa ring of balls introduced through a passageway which is closed-off during assembly by a free plug provided with a threaded bore for the extraction of said plug.

16. A drilling bit in accordance with claim 15, wherein the irrigation fluid is directed towards the working face by a discharge nozzle which is screwed within the central duct of the shaft.

17. A drilling bit in accordance with claim 16, wherein the discharge nozzle clamps in a reversible manner the plug which serves to close-off the passageway for insertion of the keying balls. 

1. A bit for drilling wells in the earth, of the type comprising a cylindrical roller having a diameter smaller than the diameter of the drilled hole and larger than the radius of said hole, a flat cutting face on said roller said roller perpendicular to the axis of said roller, irrigated destruction means on said face, armed teeth for said roller around its perimeter said roller being surmounted on the external cylindrical surface by segments which are protected against wear by anti-abrasive elements, said roller being mounted to rotate freely on a tubular shaft having a geometrical axis which is parallel to that of the drilled hole and displaced off-centre with respect to said hole, a connector, a tensioning member maintaining said connector in said geometrical axis, said shaft being connected parallel to the axis of; and in angularly positioned relation with said connector, said connector having a geometrical axis which coincides with the axis of the drilled hole, a duct in said connector for the irrigation of the bit, means at the end of said connector remote from the tool for coupling with the drill stem, external eccentric masses on said connector protected against wear on the peripheral face thereof by anti-abrasive elements, said masses centering said connector within the drilled hole, compensating for the reversing couple exerted by the bit on said connector shaft during drilling and providing static and dynamic balancing of the tool-connector assembly during the drilling operation.
 2. A drilling bit in accordance with claim 1, wherein the cutting face of the roller is irrigated from an axial duct.
 3. A drilling bit in accordance with claim 1, wherein the drilling face is armed with inset diamonds.
 4. A drilling bit in accordance with claim 1, wherein the cutting face is armed with inserts of anti-abrasive material.
 5. A drilling bit in accordance with claim 1, wherein the cutting face is armed with a diamond concretion.
 6. A drilling bit in accordance with claim 1, wherein the peripheral teeth are armed with anti-abrasive built-up portions.
 7. A drilling bit in accordance with claim 1, wherein the armour of the peripheral teeth comprises diamonds.
 8. A drilling bit in accordance with claim 1, wherein the armour of the peripheral teeth comprises anti-abrasive inserts.
 9. A drilling bit in accordance with claim 1, wherein the rotary roller is mounted on the shaft by means of thrust-bearings and ball-bearings.
 10. A drilling bit in accordance with claim 1, wherein the ball-bearings and thrust-bearings work in a bath of lubricant in pressure equilibrium with the surrounding fluid from which said bearings are isolated by means of two rotary seals.
 11. A drilling bit in accordance with claim 1, wherein the shaft of the tool is secured in the body of said connector by two superposed cylindrical bearing elements displaced in eccentric relation to each other.
 12. A drilling bit in accordance with claim 1, wherein the tensioning member is put under tension by means of a locking nut which is accessible from that end of the connector which is remote from the roller.
 13. A drilling bit in accordance with claim 1, wherein said masses are two balancing weights protected against abrasion and located at angles of 120* and 240* from the generating-line of contact of the roller with the wall of the drilled hole.
 14. A drilling bit in accordance with claim 13, wherein said weights are distributed to provide static and dynamic balancing of the roller and the connector assembly.
 15. A drilling bit in accordance with claim 1, wherein the roller is keyed on its shaft by means of a ring of balls introduced through a passageway which is closed-off during assembly by a free pLug provided with a threaded bore for the extraction of said plug.
 16. A drilling bit in accordance with claim 15, wherein the irrigation fluid is directed towards the working face by a discharge nozzle which is screwed within the central duct of the shaft.
 17. A drilling bit in accordance with claim 16, wherein the discharge nozzle clamps in a reversible manner the plug which serves to close-off the passageway for insertion of the keying balls. 